System for controlling marine craft with steerable drives

ABSTRACT

A system for controlling one or more propulsion devices of a marine vessel. The system includes circuitry configured to: receive a steering angle command for a propulsion device of the marine vessel; receive a trim position of the propulsion device; and generate a steering actuator position command for the propulsion device based on the steering angle command and the trim position of the propulsion device.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 62/048,792, entitled “SYSTEM FOR CONTROLLING MARINE CRAFT WITHSTEERABLE DRIVE” filed on Sep. 10, 2014 under Attorney Docket No.V0186.70020US00, which is herein incorporated by reference in itsentirety. This application is related to U.S. patent application Ser.No. 13/241,192, which is hereby incorporated by reference in itsentirety.

TECHNICAL FIELD

The present disclosure relates to marine vessel propulsion and controlsystems.

BACKGROUND

Various forms of propulsion have been used to propel marine vessels overor through the water. One type of propulsion system comprises a primemover, such as an engine or a turbine, which converts energy into arotation that is transferred to one or more propellers having blades incontact with the surrounding water. The rotational energy in a propelleris transferred by contoured surfaces of the propeller blades into aforce or “thrust” which propels the marine vessel. As the propellerblades push water in one direction, thrust and vessel motion aregenerated in the opposite direction. Many shapes and geometries forpropeller-type propulsion systems are known.

Other marine vessel propulsion systems utilize waterjet propulsion toachieve similar results. Such devices include a pump, a water inlet orsuction port and an exit or discharge port, which generate a waterjetstream that propels the marine vessel. The waterjet stream may bedeflected using a “deflector” to provide marine vessel control byredirecting some waterjet stream thrust in a suitable direction and in asuitable amount.

A requirement for safe and useful operation of marine vessels is theability to steer the vessel from side to side. Some systems, commonlyused with propeller-driven vessels, employ “rudders” for this purpose.Other systems for steering marine vessels, commonly used inwaterjet-propelled vessels, rotate the exit or discharge nozzle of thewaterjet stream from one side to another. Such a nozzle is sometimesreferred to as a “steering nozzle.” Hydraulic actuators may be used torotate an articulated steering nozzle so that the aft end of the marinevessel experiences a sideways thrust in addition to any forward orbacking force of the waterjet stream. The reaction of the marine vesselto the side-to-side movement of the steering nozzle will be inaccordance with the laws of motion and conservation of momentumprinciples, and will depend on the dynamics of the marine vessel design.

It is understood that while particular control surfaces are primarilydesigned to provide force or motion in a particular direction, thesesurfaces often also provide forces in other to directions as well.Nonetheless, those skilled in the art appreciate that certain controlsurfaces and control and steering devices have a primary purpose todevelop force or thrust along a particular axis. For example, in thecase of a reversing deflector, it is the backing direction in whichthrust is provided. Similarly, a rudder is intended to develop force atthe stern portion of the vessel primarily in a side-to-side or athwartships direction, even if collateral forces are developed in otherdirections. Thus, net force imparted to a marine vessel should be viewedas a vector sum process, where net or resultant force is generally thegoal, and other smaller components thereof may be generated in otherdirections at the same time.

As noted above, a class of marine craft is propelled by multiplesteerable propeller drives. FIGS. 1A-1C illustrate various views of astern/out drive that can be used in combination and FIGS. 1D-1Eillustrate various views of a surface drive 111 that can be used incombination as outboard motors. As these terms may be usedinterchangeably herein, the use of one term shall not imply that thescope of this disclosure is limited to one specific type of drive. Thescope of this disclosure includes twin-drive systems, as well as systemscomprising more than two drives. A quad-arrangement employing fourdrives, wherein a pair of drives is installed on each of two hulls of acatamaran hull form, is but one example of a system that can benefitfrom this disclosure.

A notional single-drive system is depicted in FIGS. 2A-2B, and anotional twin-drive system is shown in FIGS. 2C-2D. The twin-drivesystem illustrated in FIGS. 2C-2D comprise a port stern drive 205 andstarboard stern drive 206 and a mechanical link known as a tie-bar 207.The primary purpose of the tie bar 207 is to prevent the closely-spaceddrives 205, 206 from colliding into each other in order to avoid damageto the craft or injury or death to persons onboard.

Referring to FIGS. 3A-3B, in systems employing surface drives orventilating propellers, the propellers 310, 311, 314 and 315 can bepartially submerged for varying amounts of time, during which time thepropellers can develop substantial lateral (athwartships) and verticalforces. In multiple-drive installations of this kind, the rotation ofthe at least two of the propellers typically opposes each other. When atie bar is used in these installations, a substantial net force isexerted on the tie-bar due to the substantially equal and oppositelateral forces generated by the propellers. For example, as shown inFIG. 3A, tie bar 312 undergoes outward tension 313 when the propellers310, 311 are outboard rotating; also as shown in FIG. 3B, tie bar 316undergoes compression forces 317 if the propellers 314, 315 are toinboard rotating. By virtue of the tie-bar connection, the lateralforces are substantially cancelled out and the steering drives are notsubjected to any significant load associated with the lateral forcecomponent of the partially submerged propellers.

In view of the above discussion, and in view of other considerationsrelating to design and operation of marine vessels, it is desirable tohave a marine vessel control system which can provide thrust forces in aplurality of directions, and which can control thrust forces in a safeand efficient manner.

SUMMARY

Some embodiments provide for a system for controlling one or morepropulsion devices of a marine vessel. The system comprises circuitryconfigured to: receive a steering angle command for a propulsion deviceof the marine vessel; receive a trim position of the propulsion device;and generate a steering actuator position command for the propulsiondevice based on the steering angle command and the trim position of thepropulsion device.

Some embodiments provide for a method for controlling one or morepropulsion devices of a marine vessel. The method comprises: receiving asteering angle command for a propulsion device of the marine vessel;receiving a trim position of the propulsion device; and generating asteering actuator position command for the propulsion device based onthe steering angle command and the trim position of the propulsiondevice.

Some embodiments provide for a system comprising circuitry configuredto: receive a steering actuator position of a steering actuator coupledto a propulsion device of the marine vessel; receive a trim position ofthe propulsion device; and determine a steering angle of the propulsiondevice based on the steering actuator position and the trim position.

Some embodiments provide for a method comprising: receiving a steeringactuator position of a steering actuator coupled to a propulsion deviceof the marine vessel; receiving a trim position of the propulsiondevice; and determining a steering angle of the propulsion device basedon the steering actuator position and the trim position.

Some embodiments relate to a computer readable medium having storedthereon instructions, which, when executed by a processor, perform sucha techniques/methods.

The foregoing summary is provided by way of illustration and is notintended to be limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a top view of an outboard drive that can be used incombination with embodiments disclosed herein;

FIG. 1B illustrates a side view of the outboard drive of FIG. 1A;

FIG. 1C illustrates a rear view of the outboard drive of FIG. 1A;

FIG. 1D illustrates a side view of the surface drive that can be used incombination with embodiments disclosed herein;

FIG. 1E illustrates a top view of an surface drive of FIG. 1D;

FIGS. 2A-2B illustrate rear view and top view of a marine vessel havinga single outdrive;

FIGS. 2C-2D illustrate rear view and top view of a marine vessel havingdual outdrives and a tie-bar;

FIGS. 3A-3B illustrate forces generated on the tie bar by the dualoutdrives of FIGS. 2A-2B; FIGS. 4A-4B are exemplary maneuvering diagramsillustrating movements that can be accomplished with a marine vesselconfigured with applicant's own joystick controller system and dualwaterjets;

FIGS. 5A-5B are exemplary maneuvering diagrams illustrating movementsthat can be accomplished with a marine vessel configured withembodiments of this disclosure and dual outboard drives;

FIGS. 6A-6B illustrate an embodiment of guards according to thisdisclosure that can be used with a marine vessel configured with dualoutboard drives;

FIGS. 7A-7B illustrate an embodiment of a sliding bar according to thisdisclosure that can be used with a marine vessel configured with dualoutboard drives;

FIGS. 8A-8C illustrate an embodiment of a variable length tie-baraccording to this disclosure that can be used with a marine vesselconfigured with dual outboard drives;

FIG. 9 illustrates an embodiment of a hydraulic locking system variablelength tie-bar according to this disclosure that can be used with amarine vessel configured with dual outboard drives;

FIG. 10 illustrates an embodiment of a hydraulic system that can be usedwith the hydraulic variable length tie-bar of FIG. 9;

FIGS. 11A and 11B illustrate an embodiment of a control system that canbe used with the hydraulic variable length tie-bar of FIG. 9;

FIG. 12 illustrates various joystick control zones and movements;

FIG. 13 illustrates an embodiment a control system and process for Zone1 of the joystick controller of FIG. 12, which can be used withsteerable propellers and a trolling gear;

FIG. 14 illustrates an embodiment a control system and process for Zone2 of the joystick controller of FIG. 12, which can be used withsteerable propellers and a trolling gear;

FIG. 15 illustrates an embodiment a control system and process for Zone3 of the joystick controller of FIG. 12, which can be used withsteerable propellers and a trolling gear;

FIG. 16 illustrates an embodiment a control system and process for Zone4 of the joystick controller of FIG. 12, which can be used withsteerable propellers and a trolling gear;

FIG. 17 illustrates an embodiment a control system and process for Zone5 of the joystick controller of FIG. 12, which can be used withsteerable propellers and a trolling gear;

FIG. 18A shows a top view of a propulsion device connected to a steeringactuator that is connected to a transom of a marine vessel at a positionabove the trimming pivot point of the propulsion device;

FIG. 18B shows a side view of the propulsion device of FIG. 18A;

FIG. 19 illustrates a control system configured to control propulsiondevices of a marine vessel based, at least in part, on respective trimpositions of the propulsion devices;

FIG. 20 illustrates another control system configured to controlpropulsion devices of a marine vessel based, at least in part, onrespective trim positions of the propulsion devices; and

FIGS. 21A and 21B illustrate an indication system configured to provideindication of steering angles of propulsion devices to an operator of amarine vessel.

DETAILED DESCRIPTION

Prior to a detailed discussion of various embodiments of the presentdisclosure, it is useful to define certain terms that describe thegeometry of a marine vessel and associated propulsion and controlsystems. A marine vessel has a forward end called a bow and an aft endcalled a stem. A line connecting the bow and the stern defines an axishereinafter referred to the marine vessel's major axis. A vector alongthe major axis pointing along a direction from stem to bow is said to bepointing in the ahead or forward direction. A vector along the majoraxis pointing in the opposite direction (180° away) from the aheaddirection is said to be to pointing in the astern or reverse or backingdirection.

Any axis perpendicular to the major axis is referred to herein as a“minor axis.” A vessel has a plurality of minor axes, lying in a planeperpendicular to the major axis. Some marine vessels have propulsionsystems which primarily provide thrust only along the vessel's majoraxis, in the forward or backward directions. Other thrust directions,along the minor axes, are generated with awkward or inefficientauxiliary control surfaces, rudders, planes, deflectors, etc.

The axis perpendicular to the marine vessel's major axis and nominallyperpendicular to the surface of the water on which the marine vesselrests, is referred to herein as the vertical axis. The vector along thevertical axis pointing away from the water and towards the sky definesan up direction, while the oppositely-directed vector along the verticalaxis pointing from the sky towards the water defines the down direction.It is to be appreciated that the axes and directions, e.g. the verticalaxis and the up and down directions, described herein are referenced tothe marine vessel. In operation, the vessel experiences motion relativeto the water in which it travels. However, the present axes anddirections are not intended to be referenced to Earth or the watersurface.

The axis perpendicular to both the marine vessel's major axis and avertical axis is referred to as an athwartships axis. The directionpointing to the left of the marine vessel with respect to the aheaddirection is referred to as the port direction, while the oppositedirection, pointing to the right of the vessel with respect to theforward direction is referred to as the starboard direction. Theathwartships axis is also sometimes referred to as defining a transverseor “side-to-side” force, motion, or displacement. Note that theathwartships axis and the vertical axis are not unique, and that manyaxes parallel to said athwartships axis and vertical axis can bedefined.

The marine vessel may be moved forward or backwards along the majoraxes. This motion is usually a primary translational motion achieved byuse of the vessels propulsion systems when traversing the water asdescribed earlier. Other motions are possible, either by use of vesselcontrol systems or due to external forces such as wind and watercurrents. Rotational motion of the marine vessel about the athwartshipsaxis which alternately raises and lowers the bow and stern is referredto as pitch of the vessel. Rotation of the marine vessel about its majoraxis, alternately raising and lowering the port and starboard sides ofthe vessel to is referred to as roll. Finally, rotation of the marinevessel about the vertical axis is referred to as yaw. An overallvertical displacement of the entire vessel 10 that moves the vessel upand down (e.g. due to waves) is called heave.

In view of the above discussion, and in view of other considerationsrelating to design and operation of marine vessels, it is desirable tohave a marine vessel control system which can provide forces in aplurality of directions, and which can control thrust forces in a safeand efficient manner. The present disclosure relates to marine vesselpropulsion and control systems and more particularly to methods anddevices for controlling and allowing marine vessel steering drives tomove freely with respect to each other but to also prevent such steeringdrives from contacting each other. The disclosure also relates to acontrol system and method configured to receive at least a first vesselcontrol signal corresponding to any of a rotational movement command, atranslational movement command, and a combination of a rotationalmovement and a translational movement commands, and configured togenerate at least a first steerable drive actuator control signal and asecond steerable drive actuator control signal to control the firststeerable drive and the second steerable drive to provide the fixeddistance between the first and second steerable drives and so as toindividually control the first steerable drive and the second steerabledrives and allow the so the first steerable drive and the secondsteerable drive to move relative to each other. The disclosure alsorelates to the control system and method also configured to induce a netforce to the marine vessel substantially in a direction of the firstvessel control signal that corresponds to a combination of atranslational thrust command and a rotational thrust command, for allcombinations of the rotational and translational thrust commands. Thedisclosure is illustrated in connection with propulsion systemscomprising first and second steerable drives, particularly first andsecond outboard drives. However it is to be understood that some or allaspects of the present disclosure apply to systems using equivalent orsimilar components and arrangements, such as waterjet propulsion systemsand systems using various prime movers not specifically disclosedherein.

Referring to FIGS. 4A and 4B, there is illustrated an exemplarymaneuvering diagram as described in U.S. Pat. No. 7,601,040 B2corresponding to a joystick control system disclosed in the U.S. Pat.No. 7,601,040 B2 patent, that can be deployed on a waterjet-propelledcraft. A primary challenge in achieving similar capability in marinecraft equipped with steerable propellers and various other types ofdrives is that the drives are decoupled, which present a high risk thatthe propellers will contact each other and cause damage when controllingthe steerable drives individually.

Thus, there is a need for a system to enhance the performance of marinecraft fitted with multiple steerable propellers to eliminate the risk ofcontact of the propellers and that also provides for individual controlof the steerable drives. It is appreciated that the high-speed andlow-speed performance of a marine craft (planing type or otherwise)fitted with multiple steerable drives can be improved by decoupling thesteering control of each drive such that the steering function of eachdrive is independently controlled with a separate actuator. The variousembodiments of the system(s) disclosed herein facilitate individualcontrol of each steerable drive, thereby rendering a propulsion systemwith greater degrees of freedom and which can take full advantage of ajoystick maneuvering system or other means of control, whereby variableforce vectors can be developed. Such individual control and forcevectoring capability, not otherwise achievable when steerable drives aremechanically linked such that the drives remain substantially parallelto each other irrespective of the steering angle, enhances maneuveringperformance. The various embodiments of a system disclosed herein allowthe drives to move freely while preventing the drives from contactingeach other.

If the two or more drives are decoupled such that the steering angle ofeach drive can be controlled independently, many of the controlalgorithms and resulting features and advantages of the systems andmethods disclosed in U.S. Pat. Nos. 7,052,338; 7,037,150; 7,216,599;7,222,577; 7,500,890′; 7,641,525; 7,601,040; 7,972,187; and publishedU.S. patent application Ser. Nos. 11/960,676; 12/753,089, which areherein incorporated by reference in their entirety, can be achieved. Inparticular, FIGS. 42 and 43 of patent U.S. Pat. No. 7,601,040 B2 shows aseries of maneuvers that can be achieved by individually controllingintegral nozzle/reversing bucket devices. As described in column 42 andshown in FIGS. 44-48 (example steerable propeller control algorithm) ofthe same application, similar thrust vectoring results can be achievedby using steerable propellers instead of waterjets.

As an example, replacing the conventional tie bar with one of theembodiments disclosed herein enables a joystick system or otherelectronic control system to maneuver a dual steerable propeller drivencraft in accordance with the maneuvering diagram depicted in FIGS. 5Aand 5B, which illustrate the movements of the craft corresponding tovarious positions of the joystick and tiller (or steering wheel). Themaneuvering diagram depicted in to FIGS. 5A and 5B reflects thecapabilities of a joystick control system with underlying controlalgorithms incorporating a trolling gear summarized in FIGS. 12-17. Toaid in disclosing the control algorithms with trolling gearfunctionality included, FIG. 12 defines five control zones (1-5) interms of joystick position, and FIGS. 13-17 present the steerablepropeller control algorithm signal diagram for Zones 1-5, respectively.

One problem with decoupling the steering control of drives located inclose proximity to each other is the potential for the drives to collideand interfere with one another. While the electronic control system can,in principle, be configured to prevent a collision under normaloperating conditions, the risk that the drives will collide becomesunacceptable in the event that the control system malfunctions or one orboth of the drives is manually overridden. For this reason, a tie-bar istypically installed.

A solution to the problem of preventing colliding of adjacent driveswhile providing freedom to independently steer the drives is to installa device that allows the drives to move freely while preventing theclearance between the drives from dropping below a certain minimumvalue. One embodiment comprises a mechanical guard or bumper installedon one or multiple drives such that the guard(s) make contact when acertain minimum clearance is attained, thereby preventing any sensitivecomponents, such as the propeller, from making contact. The guards wouldbe designed to take the full force of the actuating system withoutharming any part of the drive. An example of this type of arrangement isillustrated in FIG. 6A (drives parallel) and FIG. 6B (drives positionedinward), in which port bumper guard 602 and starboard bumper guard 603is mounted to port drive 205 and starboard drive 206, respectively. Itis to be appreciated that various alterations, modifications, andimprovements of the example shown in FIGS. 6A-B will occur to thoseskilled in the art. Such alterations, modifications, and improvementsare intended to be part of this disclosure and are intended to be withinthe scope of the system disclosed herein.

Another embodiment comprises a sliding apparatus located in between andattached to adjacent drives and incorporating a mechanical stop toprevent the clearance between the drives from dropping below a certainvalue. The device may consist of two or more members (which may or maynot be connected) that are allowed to move or rotate with respect toeach other, and which incorporates one or more mechanical stops toprevent the clearance between propellers and other critical componentsfrom dropping below a certain value. One embodiment consists oftelescoping concentric tubes installed between adjacent drives, whichare attached to each end of the sliding apparatus by means of aconnection such as a pin or ball joint A mechanical stop built into thesliding apparatus prevents the clearance between adjacent drives fromdropping below a certain value. Another embodiment comprises a slidingbar arrangement consisting of an assembly of two or more parallel barsthat are permitted to slide relative to one another. A schematic exampleof this type of system can be seen in FIG. 7A (drives parallel) and FIG.7B (drives positioned inward), in which sliding bar assembly 701comprises rod 702 and tube 703, port attachment (joint) 704 andstarboard attachment (joint) 705. Yet another embodiment consists of twomembers flexibly joined together to allow rotation with respect to eachother, with the free end of each member flexibly joined to a drive,wherein relative rotation of the two members results in varyingdistances between the two free ends; a means to limit the relativerotation, such as a mechanical stop, would be provided to prevent theclearance between drives from dropping below a certain value. Variationsof these implementations include but are not limited to thoseincorporating alternate means of attachment, for example, a compoundclevis (allowing two rotational degrees freedom) or a ball joint(allowing three rotational degrees of freedom). Other variations ofthese implementations include but are not limited to those incorporatingalternate means of achieving variable distance between the drives, forexample, a hydraulic cylinder deployed in any number of ways tofacilitate the functionality described above. It is to be appreciatedthat various alterations, modifications, and improvements of the exampleshown in FIGS. 7A-B and embodiments described herein will occur to thoseskilled in the art. Such alterations, modifications, and improvementsare intended to be part of this disclosure and are intended to be withinthe scope of the system disclosed herein.

In the typical surface-drive or ventilating propeller application, thepropellers can be partially submerged for varying amounts of time,during which time the propellers develop substantial lateral(athwartships) and vertical forces. In most of these kinds ofmultiple-drive installations, the rotation of at least two of thepropellers opposes each other. When a tie bar is used in theseinstallations, a substantial net force is exerted on the tie-bar(tension if outboard rotation, compression if inboard rotation) due tothe substantially equal and opposite lateral forces generated by thepropellers. By virtue of the tie-bar connection, the lateral forcetransferred to the hull by an individual drive is minimized, and thesteering cylinder(s) is not subjected to significant load associatedwith the lateral force component of the partially to submergedpropellers.

On account of the lateral forces induced by the surface propeller(discussed above), removing the tie-bar that would otherwise nullify thelateral forces will necessitate the individual steering cylinders tocounter the forces of each individual drive. In such an arrangement, themechanical loading of the steering cylinders will likely be increasedsubstantially, and in many cases, the standard mechanical and hydrauliccomponents that are normally equipped with the drive will beinadequately sized to counter the load in a steady and/or dynamiccondition. In these cases it would be useful to have a variable-lengthor variable-geometry tie-bar that is locked in conditions when thelateral force on an individual propeller is substantial and unlocked(such that the drives could be controlled individually) when it isdesirable to move the drives relative to each other. Such an “adaptive”tie-bar could have a locking means that is mechanical (controlled via alinkage), hydraulic (controlled using a mechanical or electric valve),or electric (clutch, motor, etc.), or a combination of these methods.The adaptive (or variable-geometry lockable) tie-bar described above mayor may not incorporate a mechanical stop for the purpose of limiting theclearance between adjacent drives.

One example of a locking tie-bar implementation is the system shown inFIG. 9, where the conventional tie-bar is replaced with a hydrauliccylinder 902 operating in a passive mode, i.e., no hydraulic pump isutilized. The ends of hydraulic cylinder 902 are fitted with portattachment (joint) 913 and starboard attachment (joint) 914. When thehydraulic fluid is confined to the cylinder 902 by means of controlvalve 905 (shown in FIG. 9) in the locked position, the hydraulic lockcauses cylinder 902 to behave in the manner of a conventional tie-bar,whereby drives 901 and 910 are maintained in a fixed relationshiprelative to each other.

When one or both drives are to be moved relative to the other, forexample, when performing maneuvers such as illustrated in FIG. 5A, thehydraulic fluid is permitted to move from one side of the piston incylinder 902 to the other side by actuating control valve 905 such thatfluid is allowed to move freely between Ports P and A and Ports T and B,with any excess (make- up) fluid channeled to (from) reservoir 906,depending on the direction of stroke. Depending on the implementation ofthe control system, control valve 905 may be configured so that it is inthe closed or open position when actuated. It is to be appreciated thatvarious alterations, modifications, and improvements of the exampleshown in FIG. 9 will occur to those skilled in the art. Suchalterations, modifications, and improvements are intended to be part ofthis to disclosure and are intended to be within the scope of the systemdisclosed herein.

As discussed above, the forces that may be encountered when thepropeller is partially submerged can be quite substantial, potentiallycausing some difficulty creating the forces to move the drives when thetie-bar is unlocked. In these cases it may be advantageous to deploy adevice or some means to create tension and/or compression forces withinor in place of the tie-bar apparatus. Such a device could reduce theforces that are imposed on the individual steering cylinders, due to thefact that the applied force vector is substantially orthogonal to thedrive axis. Any of the “adaptive” tie-bar designs discussed above(mechanical, hydraulic, electric, etc.) can be combined with a means todevelop tension and or compression forces to create an “active” tie-bardevice. The active (or actuating) tie-bar described above may or may notincorporate a mechanical stop for the purpose of limiting the clearancebetween adjacent drives.

One example of an active tie-bar implementation utilizes similaroutboard components (i.e., those external to the hull) as used in theexample locking tie-bar implementation (shown in FIG. 9 and also asshown in FIGS. 8A, 8B and 8C). However, the hydraulic system for theactive tie-bar system will differ from that of the locking tie-barsystem in that the hydraulic system for the active tie-bar systemenables the active extension and retraction of active tie-bar 1001. Forexample, the hydraulic schematic for one embodiment of the activetie-bar system is shown in FIG. 10, which depicts hydraulic cylinder1001 linking port drive 1014 and starboard drive 1015. The ends ofhydraulic cylinder 1001 are fitted with port attachment (joint) 1016 andstarboard attachment (joint) 1017. In this particular implementation, inthe locked state the hydraulic fluid is locked in the cylinder by meansof counterbalance valves 1006, and the tie-bar arrangement behavessimilar to a conventional tie-bar, whereby the port and starboard drivesare maintained in a fixed relationship relative to each other. When oneor both drives are to be moved relative to the other, pressurized fluidis delivered by pump 1011 and/or 1013 to one side of the piston incylinder 1001 via port steering valve 1008 and/or starboard steeringvalve 1009, as the case may be, while fluid on the other side of thepiston is allowed to escape back to reservoir 1012.

The hydraulic system shown in FIG. 10 is one example of how anelectro-hydraulic control system could be adapted to integrate the useof an active electro-hydraulic tie-bar system. In the example shown inFIG. 10, the working ports (A & B) of steering valves 1008 and 1009 arealso connected to the Hydraulic-Actuator Tie-Bar (in addition to thesteering actuators) through two dedicated sets of counterbalance valves1006. The cylinder-side ports (A3 & B3 for STBD and A4 & B4 for PORT) ofthe dedicated tie-bar counterbalance valves are then ported to thetie-bar actuator such that actuating a single steering actuator (port orstarboard) via the respective steering valve will also actuate theHydraulic-Actuator Tie-Bar in the correct direction and not affect thesteering actuator that is not being actuated. The circuit in FIG. 10will also allow both steering valves and corresponding actuators to beactuated simultaneously. The circuit illustrated in FIG. 10 is oneexample of a hydraulic circuit designed to actuate the active tie-barsystem. It is to be appreciated that various alterations, modifications,and improvements of the example shown in FIGS. 8A-C and FIG. 10 willoccur to those skilled in the art. For example, other embodiments of theactive tie-bar may incorporate any device that can generate a suitableforce, including but not limited to hydraulic cylinders,electrically-actuated power screws, pneumatic actuators,electromechanical devices, geared mechanisms, etc., and it is understoodthat any number of configurations within a given class of actuator maybe adopted. Such alterations, modifications, and improvements areintended to be part of this disclosure and are intended to be within thescope of the system disclosed herein. One skilled in the art can modifythe circuit in numerous ways, for example, by incorporating differenttypes of valves and porting to perform the same function.

By way of example, FIG. 11 illustrates one embodiment of a systemdiagram for the device and embodiments thereof described herein.

One system and method of implementing a joystick control algorithm for adual-drive system is to separate the control algorithms into fiveseparate control zones as shown in FIG. 12, which are illustrated inmore detail in FIGS. 13-17. By separating the algorithms into distinctzones, the difference in response characteristics of the steerabledrive, for example between ahead and reverse thrust, can be compensatedfor by applying a different set of curves for the respective zones. Oneembodiment of such a system splits the control algorithms into fivedifferent zones that relate to the direction of applied nettranslational thrust: Port Thrust, Starboard Thrust, Zero Thrust(rotation only), Ahead Thrust Only (i.e., no side or reverse thrust) andAstern Thrust Only, as shown in FIG. 12. It is, of course, possible toutilize more or less than five zones, depending on the specificimplementation of algorithms and function modules. However, theunderlying goal is to create a system that compensates for thediscontinuities in the force and motion created by the combination ofpropulsion devices, including characteristics of transmission gear andassociated trolling gear (if available), in response to command oractuator inputs, for example, by changing the steering position mappingto steering wheel inputs when transitioning from ahead thrust (Zone 4)to astern thrust (Zone 5).

FIGS. 13-17 contain example algorithms for Zones 1-5 respectively.Because the effects of the propeller thrust contribute to the nettranslation and rotational thrust in different ways depending on thedirection of net translational thrust (zone), each zone has a dedicatedalgorithm such that the controller automatically updates the algorithmwhen transitioning from one zone to another. Each zone-specificalgorithm contains a different mapping that relates the control devices(e.g., joystick and steering wheel) to the propulsion devices (e.g.,steerable drive, transmission gear and associated trolling gear, engineRPM). For example, when thrusting ahead with no side thrust (Zone 4,FIG. 16), modules 1656 and 1657 turn the drives in the starboarddirection when the helm is turned to starboard (CW). In contrast, whenthrusting astern with no side thrust (Zone 5, FIG. 17), modules 1750 and1751 turn both drives to port when the helm is turned to starboard (CW).

FIG. 5A contains a maneuvering diagram (or Net Thrust Diagram) thatillustrates a plurality of thrust forces for a plurality of controllerconditions, that are provided to a vessel configured with the hereindescribed embodiment of a system and that is equipped with two steerabledrives. For example, the resulting forces imparted to the vessel for astarboard turn when thrusting ahead is shown as maneuver C. In addition,the resulting forces imparted to the vessel where the steering wheel isturned to starboard and while the craft is reversing is shown asmaneuver 0. By comparing maneuvers C and 0, one can see that in order tomaintain a clockwise rotation (bow moving in the starboard direction) ascommanded by the steering wheel (or steering tiller), the drives must bepointing in the starboard direction when thrusting ahead and in the portdirection when thrusting astern.

Referring again to FIG. 5A, the response of a vessel configuredaccording to the herein described embodiment of a system and equippedwith dual steerable propellers to CCW rotations of the wheel or tilleris shown in maneuvers A (thrusting ahead) and M (thrusting astern),respectively. It is to be appreciated that the movements of the drivesare similar to the CW turning maneuver; however, the drives turn inopposite directions, as shown in modules 1656 and 1657 for Zone 4 andmodules 1750 and 1751 for Zone 5.

Another example of control/propulsion device mapping to be considered isthe case where there is no net translational thrust (i.e., onlyrotational thrust, Zone 3). A vessel equipped with dual steerable drivesis not able to develop a turning moment by rotating the drives while atneutral thrust. Consequently, a special algorithm or mapping for theindividual drives when no translational thrust is commanded such thatthe drives can operate independently to develop the turning moment. FIG.15 shows a signal diagram for Zone 3 of the herein described embodimentof a system. It is to be appreciated that since the condition for Zone 3is zero translational thrust, the joystick inputs have been omitted fromthe diagram for simplification.

To operate in Zone 3, a control scheme must be implemented where thedrives are operated differentially, where one drive is generating aheadthrust and the other is generating astern thrust in order to impartlittle or no net translational thrust to the craft. FIG. 15 illustratesan effective method for developing rotational thrust with little or notranslational thrust. Taking for example maneuver F shown in FIG. 5A,the wheel is turned to starboard while the joystick is centered. With atrolling gear on the transmission, Module 1541 (FIG. 15) progressivelyincreases the port gear setting to achieve progressively increasingpropeller speed in the ahead direction, while module 1544 progressivelyincreases the starboard gear setting to achieve progressively increasingpropeller speed in the astern direction creating a force couple (moment)without creating a substantial net translational thrust. Since theamount of turning force created by the differential thrust of the drivesis limited while the drive steering positions are maintained in aparallel orientation at zero steer angle, additional turning of thewheel will progressively turn the port drive in the starboard direction(module 1542) and the starboard drive in the port direction (module1545). Increasingly toeing-in (pointing) the drives will increase themoment arm of the resultant force created by the two drivessignificantly while applying a relatively small side force. In additionto actuating the propeller shaft speed differentially and toeing in thedrives, modules 1540 and 1543 progressively increase engine RPM once thewheel or tiller is moved beyond a threshold point. Thus according tothis embodiment of the system disclosed herein, the system providesrotation forces with little or no translation forces by progressivelypointing in the steerable propellers and/or applying differential RPM tothe drives as a function of wheel or tiller rotation. However, it is tobe understood that the exact combination of trolling gear settings,steering angle movements, and engine RPM levels shown in the embodimentin FIG. 5A is not required to achieve the same or similar results. Forexample, the engine RPM can be increased at different points in themapping or not at all with varying levels of effectiveness. In addition,the extent of toeing in to the drives can be changed or eliminated, alsowith varying levels of effectiveness.

Vessels equipped with steerable propellers are able to inducecombinations of transverse and rotational thrusts that will allow thecraft to translate sideways while at the same time apply varying amountsof rotational thrust. As another example, referring to Zone 1 (thrustingto port) in FIG. 5A, an example maneuver in which a transverse thrust isapplied to the craft without a rotational thrust is identified asmaneuver H. The required actuation of the trolling gear, steering anglesand engine RPM to achieve maneuver H can be determined from the controldiagram of FIG. 13.

Let us first consider the case of maneuver H where the craft istranslating sideways with little or no forward or reverse thrust. Inthis case, the initial condition is maneuver E (Zone 3), in which thejoystick is centered (neutral X and neutral Y) and the steering wheel iscentered; in this condition, both transmissions will be set to neutral,in accordance with the signals created by the joystick and transmittedto modules 1300 and 1303. As the X-axis signal is increased beyond thethreshold that transitions from Zone 3 to Zone 1, the port drivesteering angle is positioned (by module 1302) in a discrete position inthe port direction and the starboard steering angle is positioned (bymodule 1305) in a discrete position in the starboard direction. Therespective positions of the port and starboard drives correspond to theequilibrium point where translational thrust can be applied in anydirection without inducing a substantial rotational or yawing force.These positions usually correspond to angles where both drives arepointed along respective center lines that intersect at or near thecenter of rotation of the craft. Drives that are positioned in thismanner are sometimes referred to as being in a toe out configuration. Aslong as the steering wheel remains in a neutral position thatcorresponds to no rotational thrust, both drives will remain in theserespective discrete positions.

As illustrated by modules 1300 and 1301, progressively moving thejoystick to increase the magnitude of net transverse thrust in the portdirection will increase the trolling gear setting (increase in frictionlevel) in the astern direction and increase the RPM of the port engine(not necessarily together), thereby increasing the reverse thrust of theport drive. At the same time, moving the joystick to port will increasethe trolling gear setting in the ahead direction and increase the RPM ofthe starboard engine, thereby increasing the ahead thrust of thestarboard drive. As long as the joystick is moved along the X-axis only(i.e., neutral Y position), the reversing thrust of the port drive andthe ahead thrust of the starboard drive will remain substantially equalin magnitude so as to induce a net transverse thrust without imparting anet to forward or reverse thrust.

Adding a rotational thrust in the port or counter-clockwise direction(maneuver G of FIG. 5A) is achieved by rotating the steering wheel inthe counter-clockwise direction. As indicated by modules 1310 and 1311,moving the steering wheel to port (CCW) will move the port drive in thestarboard direction and the starboard drive in the port direction. Thisis achieved by creating an additional starboard movement with module1310 for the port drive based on the magnitude of the wheel rotation andadding it to the discrete position output from module 1302 at summingmodule 1316. Similarly, an additional port movement is added to thestarboard drive by module 1311 and summed with the discrete output ofmodule 1305 at summing module 1317. So as not to create a situationwhere the drives are allowed to move to a point beyond the neutralposition such that the direction of translational thrust differssubstantially from the joystick movement, absolute limits are placed onthe steering movements with module 1318 for the port drive and module1319 for the starboard drive. Module 1318 will not allow the port driveto move to the starboard side of neutral (straight ahead) and module1319 will not allow the starboard drive to move to the port side ofneutral.

It is to be appreciated, however, that for cases in which there is notenough rotational thrust available in one direction as provided by thesystem described herein, the limits set by modules 1318 and 1319 can beextended.

It is to be understood that the magnitude of the steering angles of theport and starboard drives in response to steering wheel movements neednot be the same, provided there are minimal changes in translationalthrust resulting from movements of the steering wheel or tiller. Theoptimum amounts of steering angle movement for each drive in response tosteering commands depends heavily on the hydrodynamics of the craftduring side thrusting operations as well as the hull-propellerinteractions for each drive. These points can be estimated withapplication-specific modeling or determined during a sea trial.

It is understood that Zone 2 of FIG. 5A is substantially a minor imageof Zone 1, and

therefore the corresponding modules of FIG. 14 and the resultingmaneuvers J, K and L illustrated in FIG. 5A will not be discussed indetail here, for the sake of brevity.

As shown in FIG. 12, Zones 1 and 2 cover all movements of the joystickto the respective side of neutral (with respect to transverse thrust).Accordingly, the control algorithms described in FIG. 13 for Zone 1 andFIG. 14 for Zone 2 also are configured to add varying levels of aheadand astern thrust in response to joystick movements along the Y axis into order to respond to diagonal translational thrust commands from thejoystick. For example, referring now to FIG. 5B, which illustratesmovements of a vessel configured with the control system of oneembodiment of the present application and equipped with dual steerablepropellers, maneuver Q can be achieved by maintaining the steering wheelat a neutral position such that modules 1310 and 1311 (of FIG. 13) donot contribute additional steering movements to the summation modules(1316, 1317) and by moving the joystick forward in addition to the portdirection. As the joystick is moved forward along the Y axis, module1306 of FIG. 13 progressively decreases the port engine RPM and module1308 progressively increases the starboard engine RPM, therebydecreasing the astern thrust of the port drive and increasing the aheadthrust of the starboard drive. This maneuver is illustrated as maneuverQ in FIG. 5B, by schematically indicating the reduction of thrust in theport drive and the increase in thrust of the starboard drive.

In a similar fashion as maneuvers G and I illustrated in FIG. 5B, arotational thrust to port (CCW) can be added by turning the wheelcounter clockwise, thereby moving the drives towards the center as shownin maneuver P of FIG. 5B. Similarly, a clockwise rotational thrust canbe achieved by turning the wheel to starboard which will move the drivesaway from the center, as shown in maneuver R (FIG. 5B).

Like the forward diagonal movements of maneuvers Q and R in FIG. 5B,reverse diagonal thrust can be developed by moving the joystick backwardalong the Y axis. For example, by maintaining the steering wheel andmoving the joystick backwards, module 1306 30 increases the asternthrust of the port drive and module 1308 decreases the ahead thrust ofthe starboard drive. This diagonal backwards and to port maneuver isillustrated as maneuver T of FIG. 5B. In a similar fashion as maneuversG and I, a rotational thrust to port (CCW) can be added by turning thewheel counter clockwise, thereby moving the drives towards the center asshown in maneuver S of FIG. 5B. Similarly, a clockwise rotational thrustcan be achieved by turning the wheel to starboard which will move thedrives away from the center (i.e., drives splayed), as shown in maneuverU of FIG. 5B.

It is understood that Zone 2 of FIG. 5A is substantially a minor imageof Zone 1, and therefore the corresponding modules of FIG. 14 will notbe discussed in detail here for the sake of brevity.

It is to be understood that the summation modules herein described andillustrated can sum the various signals in different ways. For example,different signals may have different weights in the summation orselected signals may be left out of the summation under certainconditions. It is also the function of the summation module to clamp(limit) output signals that would otherwise exceed maximum values.

It is to be understood also that the port trolling gear moduleillustrated in FIGS. 13-17, according to the herein described embodimentof a system equipped with two steerable propellers, can be separatedinto two distinct modules to handle direction and friction level,respectively, for the port transmission. It is understood that theforegoing statement applies to the starboard trolling gear module.

As used herein, a propulsion device may be any suitable deviceconfigured to generate thrust to move a marine vessel. In someembodiments, a propulsion device may include one or more propellers(e.g., a single propeller drive or a dual propeller drive). In someembodiments, a propulsion device may include one or more waterjets. Insome embodiments, a propulsion device may include one or more pumps.Examples of propulsion devices include, but are not limited to, outboardmotors, inboard drives, outboard drives, stern drives, jet drives, andsurface drives (e.g., Arneson drives). A marine vessel may comprise oneor multiple propulsion devices.

The inventor has recognized that, in some instances, a control systemfor controlling one or more trimmable propulsion devices of a marinevessel may take into account the trim position(s) of the propulsiondevice(s) in order to more accurately control the devices in response tosteering commands. For example, as described in more detail below, acontrol system may control a propulsion device of a marine vessel based,at least in part, on the trim position of the propulsion device when asteering actuator coupled to and configured to steer the propulsiondevice is attached to the marine vessel (e.g., attached to the transomof the marine vessel) at a point that is at a different height and/or adifferent fore-aft position than the trimming pivot point of thepropulsion device.

FIGS. 18A and 18B illustrate a configuration of a trimmable propulsiondevice of a marine vessel in which control of the propulsion device maybe improved when performed based, at least in part, on its trimposition. FIGS. 18A and 18B show a top view and a side view of apropulsion device, respectively, which in this illustrative example is asurface drive 1800 having a propeller 1810. It should be appreciated,however, that the propulsion device shown in FIG. 18A and 18B is notlimited to being a surface drive and may be any other suitable type ofpropulsion device, examples of which are provided herein.

As shown in FIG. 18A, surface drive 1800 is coupled to steering actuator1820 and trim actuator 1830. Steering actuator 1820 is configured tosteer surface drive 1800 by extending or retracting. The degree ofextension of a steering actuator is referred to herein as a steeringactuator position. Trim actuator 1830 is configured to trim surfacedrive 1800 up or down about trimming pivot point 1850 by extending orretracting. The degree of extension of a trim actuator is referred toherein as a trim actuator position. The angle that a propulsion devicemakes with the major axis of the marine vessel is referred to as thesteering angle of the propulsion device. For example, when thepropulsion device is parallel to the major axis of the marine vessel,the steering angle of the propulsion device is zero degrees. As anotherexample, as shown in FIG. 18A, when the steering actuator 1820 extendsthereby moving surface drive 1800 away from a position parallel to themajor axis of the marine vessel, the steering angle of surface drive1800 is steering angle 1860.

It should be appreciated that, in some embodiments, when a marine vesselhas multiple propulsion devices, each of the multiple propulsion devicesmay be controlled independently. Accordingly, in such embodiments, thesteering actuators configured to steer respective propulsion devices maytake on different steering actuator positions from one another, thesteering angles of the propulsion devices may be different from oneanother, and/or the trim actuators configured to trim the propulsiondevices may have different trim actuator positions from one another.

In some embodiments, when a steering actuator configured to steer apropulsion device of a marine vessel is attached to the transom of themarine vessel at one or more pivot points 1870 and 1880 that are at adifferent height and/or fore-aft position than that of the trimmingpivot point of the propulsion device, trimming the propulsion device upor down while maintaining the steering angle of the propulsion devicewill require the steering actuator to retract or extend. If the steeringactuator does not retract or extend to compensate for the change in trimposition, the steering angle cannot be maintained. For example, as shownin FIGS. 18A and 18B, steering actuator 1820 is attached to the transom1840 at pivot points 1870 and 1880 that are located above and furtherforward relative to the trimming pivot point 1850 of the surface drive1800. If the surface drive 1800 is trimmed up (i.e., trimmed in thedirection of being raised out of the water) through retraction of trimactuator 1830, and the steering angle of the surface drive 1800 is to bemaintained, the steering actuator 1820 needs to retract since the pointof connection of the steering actuator 1820 to the surface drive 1800will be pulled closer to the position at which the steering actuator1820 is attached to the transom 1840 in order to maintain the samesteering angle. If the surface drive 1800 is trimmed down (i.e., in thedirection of being lowered into the water) through extension of trimactuator 1830, and the steering angle of the surface drive 1800 is to bemaintained, the steering actuator 1820 needs to extend since the pointof connection of the steering actuator 1820 to the surface drive 1800will be pushed farther from the position at which the steering actuator1820 is attached to the transom 1840 in order to maintain the samesteering angle. If the steering actuator does not extend or retract inresponse to changes in trim position, the steering angle will changewhen the trim position is changed.

When a steering actuator (e.g., steering actuator 1820) retracts orextends to accommodate a different trim position of the propulsiondevice to which it is coupled (e.g., surface drive 1800), therelationship between the extension position of the steering actuator andthe steering angle at which the propulsion device is positioned dependson the trim position of the propulsion device. If not taken into accountby a control system, this relationship may be problematic for at leastone or more of the following three reasons.

1. When the steering angle of a propulsion device is determined bymeasuring the extension position of the steering actuator configured tosteer the propulsion device (e.g., by a sensor configured to sense theextension position of the steering actuator), the measured extensionposition and, therefore, the measured sensor signal varies as a functionof trim actuator position for the same steering angle of the propulsiondevice.

2. In a marine vessel having a plurality of propulsion devices, the trimactuator position and steering actuator position for each propulsiondevice may be controlled independently. Trimming one propulsion deviceup or down relative to another propulsion device requires one or bothsteering actuator positions to change relative to one another in orderto maintain the same steering angles. When the propulsion devices areconnected by a solid tie-bar, moving the propulsion devices to differenttrim positions without adjusting the steering actuator position can puta significant stress on the tie-bar, pulling the propulsion devicestoward one another, and/or pushing the propulsion devices away from oneanother, potentially causing damage.

3. The allowable propulsion device steering arc varies depending on thetrim position of the propulsion device. For example, when the steeringactuator 1820 is extended to accommodate a particular trim position ofsurface drive 1800, full extension of the steering actuator 1820produces a different steering angle range than would be the case whenthe steering actuator 1820 is not extended to accommodate the particulartrim position of surface drive 1800. For example, as illustrated in FIG.18B, the steering actuator 1820 needs to extend when the surface drive1800 is trimmed down. When the surface drive 1820 is trimmed down and asteering command is received to turn the surface drive 1820 fully tostarboard, the maximum amount that the surface drive 1800 can be turned(i.e., the maximum steering angle of the surface drive 1800) in thatdirection is limited by the range of extension of the steering actuator1820. Since the steering actuator 1820 already needs to extend toaccommodate the lowered trim position, the amount that it can extendfurther in response to a steering angle command is limited.

For at least these reasons, a control system for controlling one or morepropulsion devices of a marine vessel may take into account the trimposition(s) of the vessel's propulsion device(s) in order to moreaccurately and/or more safely control the marine vessel. Accordingly,some embodiments provide for a control system that takes the trimposition of a propulsion device into account, when controlling thepropulsion device, by using the trim position to adjust steeringactuator commands provided for controlling a propulsion device, therebygenerating corrected steering actuator commands in order to achieve acorrected propulsion device steering angle(s).

As used herein, the term “corrected” when used to describe a steeringangle or command may refer to either the correct, actual steering angleor command, or a more accurate steering angle or command that has beencorrected in accordance with the techniques described herein.

Described herein are techniques, developed by the inventor, forcompensating for the trim position of one or more propulsion devices ofa marine vessel. In some embodiments, the system includes circuitry thatis configured to compensate for the trim position of a propulsion deviceby using the trim position of the propulsion device to adjust steeringactuator commands provided to the propulsion device. In someembodiments, the circuitry may be configured to receive a steering anglecommand for a propulsion device and a trim position (e.g., ameasured/estimated or commanded trim position) of the propulsion device,and generate a corrected steering actuator position command for thepropulsion device based on the received steering angle command and thereceived trim position. The circuitry may cause the propulsion device tobe positioned in accordance with the corrected steering actuatorposition command (e.g., by causing the steering actuator coupled to thepropulsion device to extend or retract in accordance with the correctedsteering actuator position command). In other embodiments, a separatesystem or apparatus may be used to position the steering actuator inresponse to receiving the corrected steering actuator position command.

In some embodiments, the circuitry may be configured to generate thecorrected steering actuator position command by: (1) identifying, basedon the trim position of the propulsion device, a mapping encoding adetermined relationship between steering angle commands andcorresponding corrected steering actuator position commands; and (2)using the identified mapping to generate the corrected steering actuatorposition command from the steering angle command. For example, in someembodiments, the circuitry may be configured to access a memory storinga plurality of mappings corresponding to a respective plurality of trimpositions, each of the plurality of mappings encoding a determinedrelationship between steering angle commands and corresponding correctedsteering actuator position commands. In such embodiments, the circuitrymay be configured to generate the corrected steering actuator positioncommand by: (1) identifying, based on the trim position of thepropulsion device, a mapping in the plurality of mappings; and using theidentified mapping to generate the corrected steering actuator positioncommand from the steering angle command. The mapping may be implementedas one or more look up tables, one or more parameters, one or morefunctions that may be evaluated, one or more curves, or in any othersuitable way, as aspects of the technology described herein are notlimited in this respect. In some embodiments, the circuitry may beconfigured to calculate a corrected steering actuator position commandfor a steering angle command for a propulsion device based on the trimposition of the propulsion device and the steering angle command for thepropulsion device.

FIG. 19 illustrates a control system 1900 configured to controlpropulsion devices of a marine vessel based, at least in part, onrespective trim positions of the propulsion devices. Control system 1900is configured to control port and starboard propulsion devicesindependently. Control system 1900 includes logic modules 1916, 1918,1920, and 1922 that together are configured to produce a corrected portsteering actuator position command 1910 a and a corrected starboardsteering actuator position command 1910 b in response to a vesselsteering command 1904 provided (directly or indirectly) in response tomovement of a helm 1902 or any other suitable vessel control apparatus(e.g., joystick, tiller, etc.). Each of the logic modules of controlsystem 1900 (as well as the logic modules described below with referenceto FIGS. 20, 21A, and 21B) may be implemented by any suitable circuitry,such as logic elements and/or a controller (e.g., a microprocessor), forexample.

As shown in FIG. 19, control system 1900 comprises logic module 1916configured to receive vessel steering command 1904 and produce asteering command for the port propulsion device of the marinevessel—port steering angle command 1906 a. Control system 1900 alsocomprises logic module 1918 configured to receive vessel steeringcommand 1904 and produce a steering command for the starboard propulsiondevice of the marine vessel—starboard steering angle command 1906 b. Thecommands 1906 a and 1906 b are generated without taking into account thetrim positions of the port and starboard propulsion devices,respectively. In order to generate steering actuator commands correctedfor the trim position of the port and starboard propulsion devices basedon steering angle commands 1906 a and 1906 b, control system 1900comprises logic modules 1920 and 1922. Logic module 1920 is configuredto receive port steering angle command 1906 a and port trim position1908 a, which indicates the trim position of the port propulsion device,and generate a steering actuator command corrected for the trim positionof the port propulsion device—corrected port steering actuator positioncommand 1910 a. Logic module 1922 is configured to receive starboardsteering angle command 1906 b and starboard trim position 1908 b, whichindicates the trim position of the starboard propulsion device, andgenerate a steering actuator command corrected for the trim position ofthe starboard propulsion device—corrected starboard steering actuatorposition command 1910 b.

In some embodiments, the trim position of a propulsion device may bedetermined based on one or more output(s) produced by a sensorconfigured to sense the trim position of the propulsion device. Thesensor may be configured to sense the trim actuator position of the trimactuator coupled to the propulsion device. The sensor may be integratedwith the trim actuator or propulsion device, included in the trimactuator or propulsion device, coupled to the trim actuator orpropulsion device, and/or configured to sense the trim position of thepropulsion device in any other suitable way. For example, the trimposition of steering drive 1800 may be sensed by a sensor integratedwith, included in, and/or coupled to trim actuator 1830. Accordingly, insome embodiments, port trim position 1908 a may be obtained from asensor configured to sense the trim actuator position of the trimactuator coupled to the port propulsion device, and starboard trimposition 1908 b may be obtained from a sensor configured to sense thetrim actuator position of the trim actuator coupled to the starboardpropulsion device. However, the trim position of a propulsion device maybe determined in any other suitable way and, in some embodiments, may bedetermined based on a trim actuator position control signal for the trimactuator of a propulsion device. For example, such a trim actuatorposition control signal may be provided by a trim control apparatus(e.g., a trim control knob, a joystick, etc.) in response to movement ofthe trim control apparatus by an operator of the marine vessel.Accordingly, trim positions 1908 a and 1908 b may be determined based onrespective trim actuator control signals, in some embodiments.

As described above, logic module 1920 may be configured to generatecorrected port steering actuator position command 1910 a based on portsteering angle command 1906 a and port trim position 1908 a. In someembodiments, the logic module 1920 may be configured to: (1) use porttrim position 1908 a to identify a mapping representing a determinedrelationship between received port steering angle commands and correctedport steering actuator position commands; and (2) use the identifiedmapping to obtain corrected port steering actuator position command 1910a based on port steering angle command 1906 a. The identified mappingmay be implemented as one or more look up tables, one or moreparameters, one or more functions that may be evaluated, one or morecurves, or in any other suitable way, as aspects of the technologydescribed herein are not limited in this respect.

In some embodiments, logic module 1920 may be configured to access aplurality of mappings stored in a memory and identify a mapping (fromthe plurality of mappings) to use for generating the corrected portsteering actuator command 1910 a based on port trim position 1908 a. Forexample, as shown in FIG. 19, logic module 1920 is configured to accessthree mappings represented by curves T1, T2, and T3 plotted within logicmodule 1920, each of these curves corresponding to a respective porttrim actuator position. It should be appreciated that logic module 1920is not limited to using three mappings, which are shown for clarity, andmay be configured to use any suitable number of mappings. Moreover, insome embodiments, logic module 1920 may be configured to interpolateamong stored mappings to obtain an interpolated mapping (e.g., as anaffine combination of one or more stored mappings) for a particularinput trim position of the port propulsion device.

In the plot shown within the logic module 1920, the steering anglecommand received as input to the logic module 1920 is shown on theX-axis and the corrected steering actuator position command is shown onthe Y-axis. The logic module 1920 determines the corrected steeringactuator position command 1910 a based on the identified mapping (e.g.,the identified curve) and sends the corrected port steering actuatorposition command 1910 a to additional circuitry and/or device(s)responsible for positioning the port propulsion device. The steeringactuator position command to the port propulsion device is therebycorrected for the trim position of the port propulsion device. Thecorrected port steering actuator position command 1910 a can be providedas an actuator control signal to separate control logic and/or circuitryresponsible for positioning the port steering actuator such as afeedback or full follow-up control loop or system that may or may notinclude sensors mounted on or to the steering actuators, in someembodiments. The techniques described herein are not limited to theparticular circuitry (e.g., logic, a processor, a controller, etc.) usedto implement this functionality, as those of ordinary skill in the artwill appreciate that such circuitry may be implemented in a variety ofways.

Similarly, logic module 1922 may be configured to generate correctedstarboard steering actuator position command 1910 b based on portsteering angle command 1906 b and port trim position 1908 b. In someembodiments, the logic module 1922 may be configured to: (1) use porttrim position 1908 b to identify a mapping representing a determinedrelationship between received starboard steering angle commands andcorrected starboard steering actuator position commands; and (2) use theidentified mapping to obtain corrected starboard steering actuatorposition command 1910 b based on starboard steering angle command 1906b.

In some embodiments, logic module 1922 may be configured to access aplurality of mappings stored in a memory and identify a mapping (fromthe plurality of mappings) to use for generating the corrected starboardsteering actuator command 1910 b based on starboard trim position 1908b. For example, logic module 1922 is configured to access three mappingsrepresented by curves T4, T5, and T6 plotted within logic module 1922,each of these curves corresponding to a respective starboard trimactuator position. It should be appreciated that, when the trimpositions of the port and starboard propulsion devices are the same, themappings used by logic modules 1920 and 1922 may be the same ordifferent, as aspects of the technology described herein are not limitedin this respect. Like logic module 1920, logic module 1922 is notlimited to using three mappings and may be configured to use anysuitable number of mappings. Logic module 1922 may be configured tointerpolate among stored mappings to obtain an interpolated mapping fora particular input trim position of the starboard propulsion device.

In the plot shown within the logic module 1922, the steering anglecommand received as input to the logic module 1922 is shown on theX-axis and the corrected steering actuator position command is shown onthe Y-axis. The logic module 1922 determines the corrected starboardsteering actuator position command 1910 b based on the identifiedmapping (e.g., the identified curve) and sends the corrected starboardsteering actuator position command 1910 b to the control logic,circuitry and/or device(s) responsible for positioning the starboardpropulsion device. The steering actuator position command to thestarboard propulsion device is thereby corrected for the trim positionof the starboard propulsion device. The corrected starboard steeringactuator position command 1910 b may be provided as an actuator controlsignal to separate control logic and/or circuits responsible forpositioning the starboard steering actuator such as a feedback or fullfollow-up control loop or system that may or may not include sensorsmounted on or to the steering actuators, in some embodiments. It shouldbe appreciated that although the mappings illustrated in FIG. 19 areshown using straight lines in FIG. 19, mappings used by logic modules1920 and 1922 are not limited to being linear mappings—any suitablemapping may be used.

In some embodiments, a control system that takes trim position intoaccount may be used to control the steering actuator position of eachdrive based on the trim position of both port and starboard drives. Thiscould be particularly useful to minimize stress on a solid tie-bar whenthe drives are trimmed differentially. If one drive is trimmed relativeto the other, the control system may adjust the steering actuatorposition of both drives such that substantially the same net yawingforce is maintained but the drives are moved closer or further apart toaccommodate the tie-bar movement resulting from trimming the one or bothdrives differentially. Such functionality may be implemented in thesystem described in FIG. 19, for example, by inputting the StarboardTrim Position signal 1908 b to Port Steer Actuator Position Module 1920and inputting the Port Trim Position signal 1908 a to Starboard SteerActuator Position Module 1922. Modules 1920 and 1922 may incorporate amapping method such as curves, parameters, equations, or functions thatwill adjust Port and Starboard Steer Actuator Position Commands 1910 aand 1910 b in order to accommodate the mechanical constraints imposed bythe tie-bar.

It should be appreciated that aspects of the technology described hereinare not limited to the control system 1900 described with reference toFIG. 19, and that any control system for controlling one or morepropulsion devices of a marine vessel may be modified to take trimposition(s) of the propulsion device(s) into account when controllingthe propulsion device(s). For example, trim position(s) of thepropulsion devices may be taken into account for a vessel that has acontrol system configured to control the vessel to perform rotationwithout translation, translation without rotation, or both rotation andtranslation, by way of example.

FIG. 20 shows another non-limiting example of a control system 2000configured to control propulsion devices of a marine vessel based, atleast in part, on respective trim positions of the propulsion devices.In particular, FIG. 20 illustrates a Zone 3 (rotation withouttranslation) steering control system, modified from the Zone 3 steeringcontrol system shown in FIG. 15 through the introduction of logicmodules 2025 a and 2025 b. Logic modules 2025 a and 2025 b areconfigured to adjust the steering actuator position commands for portand starboard propulsion devices of a marine vessel for a given steeringangle command based on trim position(s) of the propulsion device(s).Although Zone 3 (rotation without translation) control logic isillustrated in FIG. 20, the techniques described herein are not limitedto Zone 3 (rotation without translation) control logic and, as describedabove, the trim position may be taken into account for any steeringcontrol logic, algorithms, or system (e.g., a control logic oralgorithms configured to control the vessel to perform translationwithout rotation, rotation without translation, or both rotation andtranslation).

Control system 2000 comprises logic modules 2006, 2008, 2010, 2012,2014, 2016, 2025 a and 2025 b that are configured to control therotations per minute (RPM), gear direction, and steering angles of theport and starboard propulsion devices. Each of the logic modules ofcontrol system 2000 may be implemented by any suitable circuitry, suchas a controller (e.g., a microprocessor), for example.

As shown in FIG. 20, logic module 2006 is configured to produce portengine RPM command 2018 a in response to a vessel steering command 2004provided (directly or indirectly) in response to movement of a helm 2002or any other suitable vessel control apparatus (e.g., joystick, tiller,etc.). Logic module 2012 is configured to produce starboard engine RPMcommand 2018 b in response to vessel steering command 2004. Logicmodules 2006 and 2012 may operate as the logic modules 1540 and 1543(described above with reference to FIG. 15) operate. Logic module 2008is configured to produce port gear direction and friction level command2020 a in response to vessel steering command 2004. Logic module 2014 isconfigured to produce starboard gear direction and friction levelcommand 2020 b in response to vessel steering command 2004. Logicmodules 2008 and 2014 may operate as the logic modules 1541 and 1544(described above with reference to FIG. 15) operate.

Logic module 2010 is configured to receive vessel steering command 2004and produce a steering command for the port propulsion device of themarine vessel—port steering angle command 2022 a. Logic module 2016 isconfigured to receive vessel steering command 2004 and produce asteering command for the starboard propulsion device of the marinevessel—starboard steering angle command 2022 b. Logic modules 2010 and2016 may be configured to operate as the logic modules 1542 and 1545(described above with reference to FIG. 15) operate.

Logic modules 2010 and 2016 generate commands 2022 a and 2022 b withouttaking into account the trim positions of the port and starboardpropulsion devices, respectively. In order to account for the trimpositions of the propulsion devices, control system 2000 includes logicmodules 2025 a and 2025 b. Logic module 2025 a is configured to receiveport steering angle command 2022 a and port trim position 2024 a, whichindicates the trim position of the port propulsion device, and generatea steering actuator command corrected for the trim position of the portpropulsion device—corrected port steering actuator position command 2026a. Logic module 2025 b is configured to receive starboard steering anglecommand 2022 b and port trim position 2024 b, which indicates the trimposition of the starboard propulsion device, and generate a steeringactuator command corrected for the trim position of the starboardpropulsion device—corrected starboard steering actuator position command2026 b. Logic modules 2025 a and 2025 b may operate in any suitable wayincluding any of the ways described above with reference to logicmodules 1920 and 1922 shown in FIG. 19.

As described above, when the steering angle of a propulsion device isdetermined by sensing the extension position of a steering actuatorconfigured to steer the propulsion device (e.g., by using a sensorconfigured to sense the extension position of the steering actuator),the sensed position varies in dependence on the trim position of thepropulsion device for the same steering angle. Accordingly, someembodiments provide for correcting the steering actuator position sensedfrom a steering actuator coupled to a propulsion device based on thetrim position of the propulsion device, in order to obtain an accuratemeasurement of the steering angle of the propulsion device and/or of theposition of the steering actuator.

In some embodiments, circuitry may receive the steering actuatorposition of a steering actuator or mechanical linkage coupled to apropulsion device and the trim position of the propulsion device, andmay determine a corrected steering angle of the propulsion device basedon the steering actuator or linkage position and the trim position. Thecircuitry may be part of a control system for controlling one or morepropulsion devices of a marine vessel, part of an indication systemconfigured to provide information to operators of the marine vessel,and/or part of any other system of a marine vessel.

In some embodiments, the circuitry may determine the corrected steeringangle based on a trim position dependent mapping encoding a determinedrelationship (which may be stored in a memory or calculated inreal-time) between steering actuator positions and steering angles. Forexample, the circuitry may be configured to determine the correctedsteering angle of a propulsion device by: (1) identifying, based on thetrim position of the propulsion device, a mapping encoding a determinedrelationship between steering actuator positions and correspondingcorrected steering angles; and (2) using the identified mapping todetermine the corrected steering angle based on the received (e.g.,sensed) steering actuator position. In some embodiments, the circuitrymay be configured to access a memory storing a plurality of mappingscorresponding to a respective plurality of trim positions, each of theplurality of mappings encoding a determined relationship betweensteering actuator positions and corresponding corrected steering angles.In such embodiments, the circuitry may be configured to determine thecorrected steering angle by: (1) identifying, based on the trim positionof the propulsion device, a mapping in the plurality of mappings; andusing the identified mapping to generate the corrected steering anglefrom the steering actuator position. The mapping may be implemented asone or more look up tables, one or more parameter values, one or morefunctions that may be evaluated, one or more curves, or in any othersuitable way, as aspects of the technology described herein are notlimited in this respect.

The corrected steering angle may be used in a variety of ways. In someembodiments, the corrected steering angle may be used to controlsteering of the marine vessel. For example, the corrected steering angleof a propulsion device may be provided as a feedback signal to asteering control system. In some embodiments, the corrected steeringangle may be displayed to an operator of the vessel. For example, thecorrected steering angle may be used in an indication system of a marinevessel, which may be part of or separate from the vessel's controlsystem, to display a steering angle or steering position of thepropulsion device that is equal to or closer to the actual steeringangle or position of the propulsion device. The indication system may beany suitable type of indication system configured to provide an operatorof the marine vessel (e.g., the driver) this information, such as agauge or any other type of display (e.g., a digital or analog display).One example of such an indication system is shown in FIGS. 21A-B,described below. In yet other embodiments, the corrected steering anglesignal may be provided as an input to other systems on or off of thecraft. In some embodiments, the steering commands and/or trim commandscan be produced by software, hardware and/or firmware running a programenables controlling the marine vessel. Such a program may run ondevice(s) on the marine vessel itself or at a remote location (e.g., ina server or other computing device such as a personal computer, tabletcomputer, or other computing device). If the marine vessel is controlledby an human operator, the operator may be present in the vessel or atanother location (e.g., a remote location). The operator may control themarine vessel by operating any suitable input device, such as ajoystick, helm, or computing device (e.g., personal computer, tabletcomputer, or other device). In some embodiments, marine vessel may beautonomous, and the steering commands and/or trim commands may beproduced by software, hardware and/or firmware running a program enablescontrolling the marine vessel autonomously.

FIGS. 21A and 21B illustrate an indicator system 2100 configured toprovide indications of steering angles of port and starboard propulsiondevices to an operator of a marine vessel. The portion of the indicatorsystem illustrated in FIG. 21A includes logic module 2104 a configuredto receive port steering actuator position 2102 a and port trim position2106 a, and determine a corrected port steering angle 2108 a based onthe port steering actuator position 2102 a and the port trim position2106 a. The determined port steering angle 2108 a is then provided toport steering angle indicator 2110 a, which may be configured to providean indication of the corrected steering angle of the port propulsiondevice to an operator of the marine vessel. The portion of the indicatorsystem illustrated in FIG. 21B includes logic module 2104 b configuredto receive starboard steering actuator position 2102 b and starboardtrim position 2106 b, and determine a corrected starboard steering angle2108 b based on the starboard steering actuator position 2102 b and thestarboard trim position 2106 b. The determined starboard steering angle2108 b is then provided to starboard steering angle indicator 2110 b,which may be configured to provide an indication of the correctedsteering angle of the starboard propulsion device to an operator of themarine vessel.

In some embodiments, port steering actuator position 2102 a may besensed by a sensor configured to sense the position of the port steeringactuator. The sensor may be integrated with the port steering actuator,included in the port steering actuator, coupled to the port steeringactuator, and/or configured to sense the position of the port steeringactuator in any other suitable way. Similarly, starboard steeringactuator position 2102 b may be sensed by a sensor configured to sensethe position of the starboard steering actuator. The sensor may beintegrated with the starboard steering actuator, included in thestarboard steering actuator, coupled to the starboard steering actuator,and/or configured to sense the position of the starboard steeringactuator in any other suitable way.

In some embodiments, the port trim position 2106 a may be sensed by asensor configured to sense the trim position of the port drive. Thesensor may be integrated with the port trim actuator or drive, includedin the port trim actuator or drive, coupled to the trim actuator ordrive, and/or configured to sense the trim position of the port drive inany other suitable way. Similarly, the starboard trim position 2106 bmay be sensed by a sensor configured to sense the trim position of thestarboard propulsion device. The sensor may be integrated with thestarboard trim actuator or propulsion device, included in the starboardtrim actuator or propulsion device, coupled to the starboard trimactuator or propulsion device, and/or configured to sense the trimposition of the starboard propulsion device in any other suitable way.As described above, in some embodiments, the port and/or starboard trimpositions may be determined based on a trim actuator position controlsignal.

As described above, logic module 2104 a may be configured to generate acorrected port steering angle 2108 a based on port steering actuatorposition 2102 a and port trim position 2106 a. In some embodiments, thelogic module 2104 a may be configured to: (1) use port trim position2106 a to identify a mapping representing a determined relationshipbetween received (e.g., sensed) steering actuator positions and steeringangles; and (2) use the identified mapping to obtain a corrected portsteering angle 2108 a based on port steering actuator position 2102 a.The identified mapping may be implemented as one or more look up tables,one or more parameters, one or more functions that may be evaluated, oneor more curves, or in any other suitable way, as aspects of thetechnology described herein are not limited in this respect.

In some embodiments, logic module 2104 a may be configured to access aplurality of mappings stored in a memory and identify a mapping (fromthe plurality of mappings) to use for determining the port steeringangle 2108 a based on port trim position 2106 a. For example, as shownin FIG. 21A, logic module 2104 a is configured to access three mappingsrepresented by the curves plotted within logic module 2104 a, each ofthese curves corresponding to a respective port trim actuator position.In the plot shown within the logic module 2104 a, the steering actuatorposition received as input to the logic module 2104 a is shown on theX-axis and the corrected steering angle is shown on the Y-axis. Itshould be appreciated that logic module 2104 a is not limited to usingthree mappings and may be configured to use any suitable number ofmappings. In some embodiments, logic module 2104 a may be configured tointerpolate among stored mappings to obtain an interpolated mapping fora particular port trim position. In other embodiments, the relationshipbetween the sensed or measured actuator position and steering angle maybe calculated based on trim position of the propulsion device.

Similarly, logic module 2104 b may be configured to generate a correctedstarboard steering angle 2108 b based on starboard steering actuatorposition 2102 b and starboard trim position 2106 b. In some embodiments,the logic module 2104 b may be configured to: (1) use starboard trimposition 2106 b to identify a mapping representing a determinedrelationship between received (e.g., sensed) steering actuator positionscorrected steering angles; and (2) use the identified mapping to obtaincorrected starboard steering angle 2108 b based on starboard steeringactuator position 2102 b. The identified mapping may be implemented asone or more look up tables, one or more parameters, one or morefunctions that may be evaluated, one or more curves, or in any othersuitable way, as aspects of the technology described herein are notlimited in this respect.

In some embodiments, logic module 2104 b may be configured to access aplurality of mappings stored in a memory and identify a mapping (fromthe plurality of mappings) to use for determining the starboard steeringangle 2108 b based on starboard trim position 2104 b. For example, asshown in FIG. 21B, logic module 2104 b is configured to access threemappings represented by the curves plotted within logic module 2104 b,each of these curves corresponding to a respective starboard trimactuator position. In the plot shown within the logic module 2104 b, thesteering actuator position received as input to the logic module 2104 bis shown on the X-axis and the corrected steering angle is shown on theY-axis. It should be appreciated that logic module 2104 b is not limitedto using three mappings and may be configured to use any suitable numberof mappings. In some embodiments, logic module 2104 b may be configuredto interpolate among stored mappings to obtain an interpolated mappingfor a particular starboard trim position.

The above-described embodiments can be implemented in any of numerousways. For example, the embodiments may be implemented using hardware,software or a combination thereof. When implemented in software, thesoftware code can be executed on any suitable processor (e.g., amicroprocessor) or collection of processors, whether provided in asingle computing device or distributed among multiple computing devices.It should be appreciated that any component or collection of componentsthat perform the functions described above can be generically consideredas one or more controllers that control the above-discussed functions.The one or more controllers can be implemented in numerous ways, such aswith dedicated hardware, or with general purpose hardware (e.g., one ormore processors) that is programmed using microcode or software toperform the functions recited above.

In this respect, it should be appreciated that one implementation of theembodiments described herein comprises at least one computer-readablestorage medium (e.g., RAM, ROM, EEPROM, flash memory or other memorytechnology, CD-ROM, digital versatile disks (DVD) or other optical diskstorage, magnetic cassettes, magnetic tape, magnetic disk storage orother magnetic storage devices, or other tangible, non-transitorycomputer-readable storage medium) encoded with a computer program (i.e.,a plurality of executable instructions) that, when executed on one ormore processors, performs the above-discussed functions of one or moreembodiments. The computer-readable medium may be transportable such thatthe program stored thereon can be loaded onto any computing device toimplement aspects of the techniques discussed herein. In addition, itshould be appreciated that the reference to a computer program which,when executed, performs any of the above-discussed functions, is notlimited to an application program running on a host computer. Rather,the terms computer program and software are used herein in a genericsense to reference any type of computer code (e.g., applicationsoftware, firmware, microcode, or any other form of computerinstruction) that can be employed to program one or more processors toimplement aspects of the techniques discussed herein.

Having described various embodiments of a marine vessel control systemand method herein, it is to be appreciated that the concepts presentedherein may be extended to systems having any number or type of actuatorsand propulsion devices and is not limited to the embodiments presentedherein. Modifications and changes will occur to those skilled in the artand are meant to be encompassed by the scope of the present description.

1. A system for controlling one or more propulsion devices of a marine vessel, the system comprising: circuitry configured to: receive a steering angle command for a propulsion device of the marine vessel; receive a trim position of the propulsion device; and generate a steering actuator position command for the propulsion device based on the steering angle command and the trim position of the propulsion device.
 2. The system of claim 1, wherein the circuitry is further configured to cause a steering actuator connected to the propulsion device to extend or retract based on the steering actuator position command.
 3. The system of claim 1, wherein the circuitry is configured to generate the steering actuator position command by: identifying, based on the trim position of the propulsion device, a mapping encoding a determined relationship between steering angle commands and corresponding steering actuator position commands; and using the identified mapping to generate the steering actuator position command from the steering angle command.
 4. The system of claim 1, further comprising: a memory storing a plurality of mappings corresponding to a respective plurality of trim positions, each of the plurality of mappings encoding a determined relationship between steering angle commands and corresponding steering actuator position commands, wherein the circuitry is configured to generate the steering actuator position command by: identifying, based on the trim position of the propulsion device, a mapping in the plurality of mappings; and using the identified mapping to generate the corrected steering actuator position command from the steering angle command.
 5. The system of claim 1, wherein the circuitry is configured to generate the actuator steering position command by calculating the steering actuator position command based on the steering angle command and the trim position.
 6. The system of claim 1, further comprising: a steering actuator attached to the propulsion device and attached to a transom of the marine vessel at a different height and/or fore-aft position from a trimming pivot point of the propulsion device.
 7. The system of claim 1, wherein the circuitry is configured to receive the trim position of the propulsion device from a sensor configured to sense the trim position of the propulsion device.
 8. The system of claim 7, further comprising the sensor.
 9. A method for controlling one or more propulsion devices of a marine vessel, the method comprising: receiving a steering angle command for a propulsion device of the marine vessel; receiving a trim position of the propulsion device; and generating a steering actuator position command for the propulsion device based on the steering angle command and the trim position of the propulsion device.
 10. The method of claim 9, further comprising: causing a steering actuator connected to the propulsion device to extend or retract based on the steering actuator position command.
 11. The method of claim 9, wherein the generating comprises: identifying, based on the trim position of the propulsion device, a mapping encoding a determined relationship between steering angle commands and corresponding steering actuator position commands; and using the identified mapping to generate the steering actuator position command from the steering angle command.
 12. The method of claim 9, wherein the generating comprises: calculating the corrected steering actuator position command based on the steering angle command and the trim position. 13.-24. (canceled) 